Semiconductor manufacturing equipment and flat panel display manufacturing equipment such as LC, organic EL and inorganic EL manufacturing equipment use a halogen-base corrosive gas atmosphere. To prevent workpieces from impurity contamination, components of these equipment are made of high purity materials, and their surface purity is crucial.
The semiconductor manufacturing process uses gate etching, dielectric etching, resist ashing, sputtering, CVD and other equipment. The liquid crystal manufacturing process uses etching and other equipment for forming thin-film transistors. These manufacturing equipment are equipped with plasma generating mechanisms allowing for microfabrication with the goal of higher integration and the like.
In these manufacturing processes, many equipment utilize halogen-base corrosive gases such as fluorine and chlorine gases as the treating gas because of their reactivity. Fluorine-base gases include SF6, CF4, CHF3, ClF3, HF, NF3 and the like, and chlorine-base gases include Cl2, BCl3, HCl, CCl4, SiCl4 and the like. When radio frequency or microwaves are applied to an atmosphere filled with such gases, the gases are activated into plasmas. Since members in the equipment are exposed to the halogen-base corrosive gases or plasmas thereof, they are required to contain a minimal amount of metal other than the principal constituent material and to have high corrosion resistance.
Prior art materials capable of imparting corrosion resistance against halogen-base gases or plasmas thereof to meet these requirements include ceramics such as quartz, alumina, silicon nitride and aluminum nitride, anodized aluminum, and spray coated substrates in which the foregoing materials are sprayed to the substrate surface to form a spray coating. JP-A 2002-241971 discloses a plasma-resistant member in which a surface region to be exposed to plasma in corrosive gas is formed of a metal layer of Group IIIA in the Periodic Table having a thickness of about 50 to 200 μm.
Regrettably, the ceramic members require an increased machining cost and suffer from the problem of particles left on the surface. When the ceramic members are exposed to plasma in a corrosive gas atmosphere, corrosion gradually takes place, though to a varying extent, whereupon crystal grains spall off from the surface region, causing so-called particle contamination. Once spalling off, particles are likely to deposit on or near the semiconductor wafer, lower electrode or the like to exert negative impact on etching precision or the like, detracting from the semiconductor performance and reliability.
The ceramic members are characterized by the elimination of electric conduction and cannot be used as radio-frequency grounding members requiring electric conductivity. At the site where such characteristics are required, anodized aluminum parts are often used, but suffer from problems like a short life and release of AlF particles. At such a site, members having sprayed thereon yttrium oxide (Y2O3) having better halogen plasma resistance have been recently used.
However, the advanced plasma environment has a propensity for increasing energy, raising a problem that spark partially generates due to a tipping of the plasma balance. It is believed that the spark generation is attributed to the dielectric material which is sprayed on the surface of conductive material, and specifically, microscopic surface irregularities on the sprayed coating and open pores therein extending to the substrate. Efforts have been made to reduce the size of surface irregularities and pores, but these countermeasures are unsatisfactory.
One probable means for solving the problem is to set in a plasma environment an electrically conductive part which allows a direct current component to escape to the ground so as to avoid spark generation. There have been found no members that enable this idea.
As discussed above, JP-A 2002-241971 discloses a plasma-resistant member in which a surface region to be exposed to plasma in corrosive gas is formed of a metal layer of Group IIIA in the Periodic Table. The thickness of the metal layer is about 50 to 200 μm, but its electric resistance is described nowhere. In the semiconductor manufacturing equipment, the reaction product of the process gas with a workpiece will deposit on members in the equipment chamber, and periodic cleaning is thus needed for removal of the reaction product deposits. In the event that the corrosion resistant member is a layer of about 200 μm thick, however, this corrosion resistant layer can be readily abraded away to expose the underlying substrate during the operation of polishing and cleaning for removal of the reaction product deposits. Thus this member cannot maintain the desired corrosion resistance on repeated use.
In the current semiconductor device art, there is an increasing propensity for feature size reduction and overall diameter increase. Concomitantly, the so-called dry process, especially etching process uses low-pressure high-density plasma. As compared with conventional etching conditions, the low-pressure high-density plasma has great influence on the plasma-resistant member, making more serious the problems including erosion by plasma, contamination of member components caused by the erosion, and contamination with the reaction products of surface impurities.
In general, unwanted metal elements or impurities that cause defectives in the semiconductor manufacturing process include Na, K, Ca, Mg, Fe, Cr, Cu, Ni, Zn, Al and the like. Among others, Fe, Cu, Ni, Zn and Cr are unwanted. Accordingly, not only equipment components, but also members for securing the components have to be plasma resistant.
While metal machining tools are used for cutting, grinding and otherwise machining of members, the machined members are contaminated on their surface. When used in a halogenic plasma atmosphere, such contaminated members become the causes of particle contamination and erosion.